1. Field of the Invention
This invention relates to a magnetic head assembly in a magnetic disk device, and in particular to a magnetic head assembly which suppresses vibrations.
2. Description of the Related Art
A magnetic disk device causes a magnetic disk, comprising ferromagnetic material, to rotate, and by scanning a magnetic head over the magnetic disk records and reproduces information; such devices are widely used as auxiliary storage devices in computers.
With the expansion of magnetic disk device capacities in recent years, there has been increased need for higher recording densities. Methods of raising recording densities include methods to increase the linear recording density in the track direction, and methods to raise the recording density in the radial direction of the magnetic disk by reducing the track width and track pitch. In order to raise the recording density through the latter methods in particular, a magnetic head assembly is desired which affords high reliability and accurate positioning. However, in a magnetic disk device the high-speed rotation of the magnetic disk causes air flow, and the magnetic head assembly on which the magnetic head is mounted undergoes vibrations. In a magnetic disk device in which submicron positioning is required, the influence of air flow and vibrations makes accurate positioning difficult, and causes detracking. If detracking occurs frequently, the frequency of occurrence of data record/playback errors is increased, and the data transfer rate declines.
FIG. 1 shows the configuration of a conventional magnetic head assembly. The magnetic head i flies while maintaining a gap of nanometer order during recording and playback, to scan the magnetic disk. The magnetic head 1 is mounted on the magnetic head assembly with a flexure 2 intervening, provided so as to oppose the magnetic disk. The flexure 2 is formed for low rigidity in order to improve tracking ability of the magnetic disk 1 with respect to the magnetic disk, and comprises wiring to transmit the information received and read by the magnetic head as well as information for the magnetic head to write. The flexure 2 comprises an extremely thin leaf spring, fixed to the load beam 3 by laser welding or another means. One end of the load beam 3 supports the magnetic head by means of a dimple; the other end is joined to the actuator arm via a base plate 4. The base plate 4 is a member used to mount the magnetic head assembly on the actuator arm. The load beam 3 is a spring member which generates a load to balance the flight of the magnetic head 1; the gimbal portion 5 is a spring member which supports the magnetic head 1 and which, by elastic deformation on the plane not parallel to the disk surface, absorbs disk runout and inclination without detracting from the tracking performance. Through this construction, the magnetic head 1 can move while maintaining a stable state over a prescribed track of the rotating disk.
FIG. 2 is an enlarged drawing of the vicinity of a magnetic head. The magnetic head 1 is joined using adhesive the gimbal portion 5 of the flexure 2. The gimbal portion 5 of the flexure 2 is supported at a single point by the dimple 6 of the load beam 3.
FIG. 3 shows the joined portion of the flexure and load beam. The flexure 2 and load beam 3 are jointed by laser welding. The base plate 4 and load beam 3, and the base plate 4, load beam 3 and flexure 2 are similarly joined by laser welding.
FIG. 4 shows a configuration in which a damping material is employed in the magnetic head assembly, in order to suppress load beam torsion mode vibrations. A damping material 8 is affixed to the load beam 3, on the side of the base plate 4 from the laser-welded portion 40 of the flexure 2 and load beam 3. By this means, vibrations in the load beam 3 in the X-axis direction with the Y=0 plane as the center of symmetry can be suppressed. Suppression of vibrations through application of damping material to a load beam 3 is described in Japanese Patent Laid-open No. 5-325459.
However, although it is possible tot suppress torsion mode vibrations in the load beam 3 of a magnetic head assembly by affixing such damping material, suppression of other vibration modes cannot be expected.
Moreover, randomly affixing the damping material in a magnetic head assembly incurs increased manufacturing costs and so is undesirable. Further, efforts are made to decrease the moment of inertia with respect to rotation of the actuator arm during positioning, by for example providing holes penetrating the base plate, in order to realize rapid positioning of the magnetic head assembly. Randomly affixing damping material results in increases in the moment of inertia of rotation centered on the actuator of the magnetic head assembly, and so is undesirable.
Hence one object of the invention is to provide a method of suppression of magnetic head assembly vibrations, caused by the effects of the flow of air arising from the high-speed rotation of the magnetic disk in the magnetic disk device. A further object is to provide a method which, while suppressing such vibrations, minimizes the increase in mass of the magnetic head assembly and the increase in manufacturing costs.